Interpretive Summary: A new compound, named dinoxin B, has been isolated and identified from pricklyburr (Datura innoxia) leaves, a species which grows wild in a number of US states. Dinoxin B’s chemical structure was confirmed by a number of spectrophotometric techniques including NMR and mass spectrometry. The compound was shown to be able to kill several human breast cancer cell lines at very low levels of activity. This compound may be an effective anti cancer agent.

Technical Abstract:
A new withanolide, dinoxin B (12,21-dihydroxy-1-oxowitha-2,6,24-trienolide-27-O-'-D-glucopyranoside) (1), was isolated from a methanol extract of Datura innoxia Mill. leaves, using bioassay guided fractionation. The structure was determined by spectroscopic techniques, including 1H, 13C-NMR, and 2D-NMR experiments as well as by HR-MS. Extracts and the purified compound were tested for their anti-proliferative activities towards a panel of human normal and cancer cell lines. Dinoxin B had sub-micromolar IC50 values against several breast cancer cell lines. Dinoxin B is uniquely found in D. innoxia, it was not detected in D. metel or D. stramonium; further the accumulation of this compound was the greatest in leaf tissue, less in flowers, with little to none detected in extracts from fruit, root or stem of D. innoxia.